It has long been desirable to combine an audible message with the display of a slide transparency and in recent years various arrangements have been devised whereby the sound track for the audible message has been made part of an assemblage which also includes the slide transparency. The Kalart Kalavox (TM) and the 3M Sound-On-Slide (TM) projector are two devices which utilize sound slides for delivering both a projected visual image and an audible message from such a slide. These devices have a wide range of use in such areas as training, education and entertainment.
Most sound slides of the prior art will record and reproduce an audible message lasting from 30 to 60 seconds. They employ a plastic body which carries the sound recording material and also accepts a 24.times.36 mm transparency premounted in the conventional cardboard or plastic mount which is 2.times.2 inches and from 45 to 70 thousandths of an inch thick. The 2.times.2 inch mounted slide is readily inserted into the plastic body of the sound slide by the user. The most well-known sound slides of the prior art use either an annular sound track area surrounding the 24.times.36 mm image area or a magnetic tape chamber or cassette to one side of the 24.times.36 mm image area. Such sound slides vary in size from 31/4 .times. 31/4 inches, 25/8 .times. 43/4 inches and range from 7/32 inch in thickness to 7/16 inch in thickness.
In U.S. Patent application Ser. No. 402,168, assigned to the assignee of the present invention, simpler and more economically fabricated sound slide structure has been disclosed. The projectors for use with the present invention comprise the customary projection head consisting of a lamp, a picture gate which accepts the transparency portion of the sound slide and the projection lens, together with the sound recording and reproducing segment which scans the sound track while the associated picture is projected. Another segment of the projector feeds the slide from a magazine into the gate and the sound segment, and removes the slide, replacing it in its previous position in the magazine.
The assignee herein has disclosed sound slide projectors employing tape cassettes in U.S. Pats. Nos. 3,232,167, 3,408,139, 3,561,856, and 3,563,644, while sound slide assemblies carrying adjacent picture sections and sound record sections are disclosed in the assignees U.S. Pat. Nos. 2,961,922, 3,145,616, 3,185,773 and 3,191,494.
Although the approaches employed in the aforementioned patents to combine audible and visual messages on a common carrier have certain advantages and have been employed successfully, the applicant believes that further improvements are necessary if more satisfactory and more economical results are to be obtained. It is to such improvements that the present invention is directed.